Modulation of Tau Protein Neurotoxic Hallmarks by Novel σ1R Agonists/HDAC Inhibitor Dual-Acting Compounds

Neurodegenerative diseases, like Alzheimer's disease (AD), are characterized by the accumulation of tau aggregates, leading to neuronal dysfunction and cognitive decline. This study explores the development of dual-acting compounds combining sigma-1 receptor (σ1R) agonists and histone deacetylase inhibitors (HDACi) to target these pathological mechanisms. Compounds 2d and 3a demonstrated high affinity for σ1R and significantly reduced tau aggregation and phosphorylation in vitro, notably at the AT8 epitope. These dual-acting compounds destabilized tau aggregates, increased tau solubility, and showed favorable pharmacokinetic properties, with compound 2d exhibiting enhanced chemical stability and longer half-life than 3a. In vivo, both compounds confirmed a σ1R agonist profile by reversing the effect of the σ1R antagonist BD-1063. This dual-action approach, acting on both HDAC and σ1R pathways, holds significant potential for treating tauopathies. While further optimization and clinical evaluation are needed, these findings provide a strong foundation for the continued development of multimodal therapies for neurodegenerative diseases treatment.